TDS, mg/L, ppm, GH, HELP ME!!!!

AndyAps.com · Post by **AndyAps.com** » Mon Jan 15, 2007 2:44 pm

Hi all,
I have a new TDS meter that measure in ppm. up till now i have measured GH with a titration test kit which always comes out at moderatley to very soft water. However i have started using the TDS meter and its comming out with results that seem unbelievebly hard.
Before i always had a reading of 80-120 mg/L which is soft ( i still get that reading with the GH test kit) the TDS meter however gives a reading of 947ppm in my comunity tank and 586ppm in my breeding tank. I have been doing loads of research on the net this morning as to what these values mean and how to convert them etc but as far as i can work out
1ppm=1mg/L, which would put my water at liquid rock!! (lake malawi)
other converisons i have found are
1 ppm = 1 mg/L CaCO3
1 ppm = 0.058 grains/US gallon
1 ppm = 0.07 Clark degrees
1 ppm = 0.10 French degrees
1 ppm = 0.056 German degrees
1 French degree = 1 hydrotimetric degree
1 Clark degree = 1 grain / Imperial gallon as calcium carbonate
1 French degree = 1 part / 100,000 calcium carbonate
1 German degree = 1 part / 100,000 calcium oxide
1 grain/US gallon = 17.1 ppm
1 grain/US gallon = 1.20 Clark degrees
1 grain/US gallon = 1.71 French degrees
1 grain/US gallon = 0.958 German degrees

But depending which calculation i do depends how hard my water gets.........im either crap at maths or am missng some information.
Can anyone provide any help regarding, how do i convert my ppm figure to a workable value, ie is 586ppm soft or hard?, how do i convert it to GH? and the meaning of life?
Thanks
Andy

Post by **John** » Mon Jan 15, 2007 4:10 pm

Can you callibrate this meter?
Did you do a test in distilled or ro water and callibrationfluid?

McEve · Post by **McEve** » Mon Jan 15, 2007 4:25 pm

a killi breeder exlaining TDS

hope this helps

or this

As you can see PPM does nessesarily have anything to do with hardness. As I understand it you want a low reading of PPM in the water, like rainwater has.

TDS is the sum total of all of the dissolved things in a given body of water. It's everything in the water that's not actually water. It includes hardness, alkalinity, cyanuric acid, chlorides, bromides, sulfates, silicates, and all manner of organic compounds.

davo · Post by **davo** » Tue Jan 16, 2007 3:08 am

AndyAps.com

this web site will help

http://www.drhelm.com/aquarium/chemistry.html

and thanks for the pm.

TomSharland · Post by **TomSharland** » Tue Jan 16, 2007 8:36 pm

gH is not the only thing that affects TDS PPM. Any substance that is in solution will increase the PPM/uS reading. A TDS meter works by measuring the conductivity of the water (by running a small electrical current between two probes) the more dissolved substances in the water, be that calcium carbonate (the main compound that gives you gH), salt, sugar...etc, the easier it is for electricity to pass through water, thus a higher conductivity is noted. PPM is a conversion of this conductivity. In reality, the conductivity also depends on what is dissolved in water. eg 50ppm of salt in pure water will conduct electricity slighlty differently than 50ppm calcium carbonate in pure water. So the conversion of uS (conductivity) to PPM is only a rough estimator - usually ~50-80 % ie 100uS = ~70ppm

uS = microsiemens
mS = microsiemens
S = siemens

A good defenition of conductivity here
Conductivity converter

I hope that makes sense!

Tom

(Just to confuse the matter a little - conductivity is also temperature dependant!)

AndyAps.com · Post by **AndyAps.com** » Wed Jan 17, 2007 11:27 am

Thanks for your help everyone. I uderstand that TDS is everythin in the water from Nitrates to salt(CaCo3). I think the meter need calibrating tho as it reads RO water at 150ppm.
I would also like to express my gratitude to MARTYN and NEIL at
www.RO-MAN.co.uk
for all his help and for sending me some calibration solution FOC when he heard my problem. Many Thanks.

Has Any one ever recorded their PPM daily throughout a spawning to give an overview of the spawning conditions, as this is what im planning to do over my next spawn. I plan to measure TDS, GH, KH, PH, Nitrate and input this into a spread sheet to give a sort of spawning overview story. if anyone has done this before id love a PM.
Thanks
Andy

smithrc · Post by **smithrc** » Wed Jan 17, 2007 12:12 pm

I dread to think what my tank stats are at at the moment - its now been 8 weeks since the last water change (as I didnt want to disturb the new spawn)

I might have a test tonight and post it up.